Logging in a Web App (Threads, Sessions and Requests)

[Hart, Leo]

Title: Message

I have a Log4Net problem/situation that I'm sure many of you have come across and have (hopefully) overcome.  I scoured the 'net for an answer but wasn't able to find exactly what I needed.

 

I'm starting to use Log4Net in my web application and I'm quite pleased with it overall.  I was a user of Log4J when I was programming J2EE apps, so obviously Log4Net is a comfortable fit. 

 

I've embedded log statements throughout the various tiers of my enterprise app and it's outputting useful information to my rolling log file just fine.  The problem is when the app leaves my development machine and moves to a production server with multiple users hitting it at once.  At that point it becomes very difficult to identify which log entries pertain to which users. 

 

So obviously I want to embed the session ID and/or the request ID in my log entry.  The first thing that came to mind was to simply log the session/request IDs in the Page_Load/Page_Unload event, but that doesn't work because the other log entries that occur in between Page_Load and Page_Unload won't have that info. 

 

The next thing that came to mind was MDC/NDC.  The problem with that is that MDC/NDC seems to be thread-based and since a given IIS server thread can support multiple sessions at once, the sessionID MDC can be overwritten.  I realized this fact once I coded the following in my global.asax:

 

Sub Session_Start(ByVal sender As Object, ByVal e As EventArgs)
    ' Fires when the session is started

    log4net.MDC.Set("sessionID", Session.SessionID)

    m_log.Info("Session " & Session.SessionID & " is starting.")
End Sub

Sub Session_End(ByVal sender As Object, ByVal e As EventArgs)
    ' Fires when the session ends

    log4net.MDC.Remove("sessionID")

    m_log.Info("Session " & Session.SessionID & " has ended.")
End Sub

The last approach that came to mind was making the MDC.Set/Remove calls in my ASPX page in the Page_Load/Page_Unload events, but that might not work either given that, once again, multiple sessions are in each thread.  Things would get especially confusing if I turned on logging in not only my presentation tier, but my business tier, my data tier and any third party assemblies I'm utilizing.

 

So what do I do?  How do I solve this problem?  CAN I solve this problem?

 

 

Thanks for your time...

Leo Hart